The National Hurricane Center on Monday night made the change after seeing reports from an NOAA Hurricane Hunter reconnaissance aircraft that indicated the storm had hurricane-force winds.

View full sizeHurricane Cristobal was expected to pass west of Bermuda on Wednesday. (National Hurricane Center)

Cristobal had estimated winds of 75 mph on Monday, the hurricane center said. The threshold for hurricane status is 74 mph, according to the Saffir-Simpson scale.

Even the hurricane center acknowledged Cristobal's unlikely ascendance to a hurricane in its forecast discussion late Monday: "Similar to Hurricane Bertha earlier this year in roughly the same location, this system's cloud pattern does not resemble that of a hurricane, with little or no evidence of banding on satellite images."

However, Cristobal was expected to strengthen a little more as it moved deeper into the Atlantic.

As of 10 p.m. CDT Monday, Hurricane Cristobal was located about 655 miles southwest of Bermuda, and was moving north-northeast at 2 mph.

A tropical storm watch was in effect for Bermuda. Cristobal was expected to pass to the northwest of the island on Wednesday.

The new hurricane moved erratically on Monday, but the hurricane center expects it to turn to the north-northeast overnight, then pick up speed and move northeast on Tuesday.

Because Cristobal has been moving so slowly, a flood threat still remains for portions of the Bahamas and Turks and Caicos Islands through Tuesday, the hurricane center said.

View full sizeIn addition to Cristobal, forecasters are monitoring two other tropical waves in the Atlantic. (National Hurricane Center)

Meanwhile, there were two other tropical waves that forecasters are watching.

The first, Invest 97L, was located about 1,100 miles east of the Lesser Antilles Monday night and was moving west-northwest at 15 mph.

It had virtually no shot at strengthening until the end of the week, the hurricane center said, but then conditions could become more favorable for development.

The second wave hasn't even moved off the coast of Africa yet.

The hurricane center said it would emerge into the Atlantic by the weekend and could develop further.

Cristobal is the third hurricane of 2014 in the Atlantic. The first was Arthur, a Category 2 storm when it made landfall in North Carolina in early July. Next was Bertha, which was briefly a hurricane and brushed Puerto Rico and the Bahamas before recurving out to sea in early August.